"It doesn't like to be taken care of. It's difficult to bond with since it won't listen to its Trainer. Because it is very proud, it hates accepting food from people. Its thick down guards it from cold. A skilled swimmer, it dives for over 10 minutes to hunt."
Piplup first appeared when it was given to Lexi as a Starter Pokémon from Professor Rowan in Sinnoh when she decided to begin her journey. Upon meeting, he seemed quite unsure of Lexi, at first seeming to disagree with going with her. When Rowan suggested she hand the Pokémon a Poffin, he quickly ate it up and agreed to go with Lexi, albeit disgruntedly. However, he remained outside of his Pokéball, refusing to be cooped up alone. Upon heading to the Sevii Islands, Piplup and Lexi would steadily begin to gain a strong and close bond quite quickly. Piplup, who enjoyed battling, begun to enjoy his encounters with Pokémon and seemed to gain a great respect for Lexi's skills. When coming into contact with a Biker Gang, Piplup jumped in to save Lexi from being ran over, showing its love for her. From then on, Piplup began to become a strong force on her team, and begun to show affection for his Trainer. Due to this, he showed signs of jealousy when it came to Lexi and her fellow Pokémon, although Piplup coped with this by becoming bossy and a father figure to the team. He stayed with her until she headed to Unova where it was left in the care of Hayley, which didn't go down well with him. However, when Lexi told him that she wanted him to be in charge of taking care of them all, he reluctantly agreed. Piplup is often shown to miss Lexi whenever Hayley comes into contact with her.
Piplup is a very proud Pokémon who likes to take himself seriously. He's a keen battler, but also loves playing around. When he's intimidated, instead of acting scared, he often becomes angry and uppity, showing signs of having a short temper, frequently getting into disagreements with other Pokémon, and Trainers. Piplup has shown to have much affection for Lexi, be it only when know one else is watching. He has also shown to be loving towards Lexi's other Pokémon, but usually veils this by being bossy and acting like it's the Leader of all her Pokémon. He seems to have a large appetite for Pokémon food and does not like having any taken away from him.
Piplup, although young, has managed to begin the art of water manipulation, creating water bubbles to throw at enemies.